(a) Field of the Invention
The present invention relates to a photosensitive material for electrophotography uses amorphous silicon as a photoconductive material. More particularly, the present invention relates to an amorphous silicon type photosensitive material for electrophotography having a specific aluminum oxide layer between a photoconductive layer and a substrate.
(b) Description of the Prior Art
Examples of photoconductive materials conventionally used in a photosensitive material for electrophotography include inorganic materials such as Se, ZnO and the like or organic materials such as poly-N-vinylcarbazole, trinitrofluorenone and the like. However, recently, amorphous silicon has attracted a good deal of attention as a photoconductive material. This is probably because a photosensitive material for electrophotography using amorphous silicon as a photoconductive layer has properties equivalent or superior to the other conventional materials. Furthermore, the amorphous silicon type photosensitive material is nonpoisonous to human and natural environments, and has very high durability.
However, the conventional amorphous silicon type photosensitive material has a disadvantage in that a deformation of layer occurs when an amorphous silicon layer is formed on a substrate, and the amorphous layer has problems such as embossing, exfoliation, cracking and the like since the adhesion between the substrate and the amorphous silicon layer is not satisfactory.
In order to solve these problems, the following methods (1) to (3) have been conventionally carried out. That is,
(1) a method of improving the adhesion between a substrate and an amorphous silicon layer by providing a crystalline silicon layer between the substrate and the amorphous silicon layer (see Japanese Patent Laid Open No. 57-44154);
(2) a method of improving the adhesion between a substrate and an amorphous silicon layer by forming aluminum oxide containing water (Al.sub.2 O.sub.3 -nH.sub.2 O; n=1, 3) on the surface of the substrate (see Japanese Patent Laid Open No. 57-104938); and
(3) a method of improving the adhesion between a substrate and an amorphous silicon layer by providing an auxiliary layer comprising nitrogen atoms between the amorphous silicon layer and the substrate.
However, the above mentioned methods (1) to (3) still have the following problems. That is,
(1) according to the method (1), it is necessary to make the temperature of the substrate very high. Therefore, the substrate is damaged, and the properties as a photosensitive material for electrophotography are deteriorated since an atom constituting the substrate diffuses into the crystalline silicon layer;
(2) according to the method (2), the pores of an aluminum oxide layer are blocked with boiling water or pressurized water vapor in an autoclave, and therefore the anchor effect of the pore is not utilized for improving the adhesion, and in the same manner as in the method (1), the properties as a photosensitive material for electrophotography are deteriorated since the OH groups and oxygen atoms of water gradually diffuse into the amorphous silicon layer; and
(3) according to the method (3), the auxiliary layer itself is hard, and exfoliation and embossing occur between the auxiliary layer and the substrate since the adhesion between the auxiliary layer and the substrate is not satisfactory.